The present invention relates to a method for processing a photoresist-coated board, a method for manufacturing a stamper for a recording medium and a method for manufacturing a recording medium which can form a fine raised and depressed pattern having a uniform width after development even in the case where a laser beam having a relatively long wavelength is used for forming pre-pits on a recording medium with high accuracy. A photoresist-coated board 108 is constituted by laminating a light absorption layer 108b and a photosensitive material layer 108c on a glass substrate 108a in this order and is exposed to a laser beam 102 by condensing the laser beam 102 onto the photosensitive material layer 108c, thereby forming a raised and depressed pattern corresponding to pre-pits on the the photosensitive material layer 108. When the length of a pre-pit to be formed is shorter than 4 T, for example, the duty ratio of the pulse signal train input to the light modulator 109 is varied within a range from about 50% to 65% so that a pulse signal train having a higher duty ratio is generated as the length of a pre-pit to be formed becomes longer and the power of a laser beam is modulated by the thus generated pulse signal train. On the other hand, when the length of a pre-pit to be formed is equal to or longer than 4 T, for example, a pulse signal train having a constant duty ratio is generated independently of the length of the pre-pit to be formed and the power of a laser beam is modulated by the thus generated pulse signal train.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A method for processing a photoresist-coated board comprising steps of intermittently projecting a pulse-like laser beam onto a photosensitive material layer on or above a light absorption layer provided in the photoresist-coated board to expose the photosensitive material layer to the laser beam, and developing the photosensitive material layer, thereby forming a raised and depressed pattern on the photosensitive material layer, wherein when a length of a depressed portion or a projecting portion of the raised and depressed pattern is shorter than a predetermined length, a duty ratio of the pulse-like laser beam is varied in accordance with the length of the depressed portion or the projecting portion of the raised and depressed pattern, and when the length of the depressed portion or the projecting portion of the raised and depressed pattern is equal to or longer than the predetermined length, the duty ratio of the pulse-like laser beam is kept constant independently of the length of the depressed portion or the projecting portion of the raised and depressed pattern, thereby exposing the photosensitive material layer to the laser beam.
2. A method for processing a photoresist-coated board comprising steps of intermittently projecting a pulse-like laser beam onto a photosensitive material layer provided in the photoresist-coated board to expose the photosensitive material layer to the laser beam, and developing the photosensitive material layer, thereby forming a raised and depressed pattern on the photosensitive material layer, wherein the method for processing a photoresist-coated board further comprises a step of varying a duty ratio of the pulse-like laser beam in accordance with a length of a depressed portion or a projecting portion of the raised and depressed pattern to be formed wherein when the length of the depressed portion or the projecting portion of the raised and depressed pattern is shorter than a predetermined length, the duty ratio of the pulse-like laser beam is varied in accordance with the length of the depressed portion or the projecting portion of the raised and depressed pattern, and when the length of the depressed portion or the projecting portion of the raised and depressed pattern is equal to or longer than the predetermined length, the duty ratio of the pulse-like laser beam is kept constant independently of the length of the depressed portion or the projecting portion of the raised and depressed pattern, thereby exposing the photosensitive material layer to the laser beam.
3. A method for manufacturing a stamper for a recording medium comprising a step of intermittently projecting a pulse-like laser beam onto a photosensitive material layer on or above a light absorption layer provided in the photoresist-coated board to expose the photosensitive material layer to the laser beam, and developing the photosensitive material layer, thereby forming a raised and depressed pattern on the photosensitive material layer and a step for transferring the raised and depressed pattern formed on the photosensitive material layer onto the stamper for a recording medium, thereby forming a raised and depressed pattern on the stamper for an optical recording medium wherein when a length of a depressed portion or a projecting portion of the raised and depressed pattern is shorter than a predetermined length, a duty ratio of the pulse-like laser beam is varied in accordance with the length of the depressed portion or the projecting portion of the raised and depressed pattern, and when the length of the depressed portion or the projecting portion of the raised and depressed pattern is equal to or longer than the predetermined length, the duty ratio of the pulse-like laser beam is kept constant independently of the length of the depressed portion or the projecting portion of the raised and depressed pattern, thereby exposing the photosensitive material layer to the laser beam.
4. A method for manufacturing a stamper for a recording medium comprising a step of forming a raised and depressed pattern on a photosensitive material layer provided in a photoresist-coated board by intermittently projecting a pulse-like laser beam onto the photosensitive material layer to expose the photosensitive material layer thereto and developing the photosensitive material layer, and a step of transferring the raised and depressed pattern formed on the photosensitive material layer onto a stamper for a recording medium and forming a raised and depressed pattern on the stamper, wherein the method for manufacturing a stamper for a recording medium further comprises a step of varying a duty ratio of the pulse-like laser beam in accordance with a length of a depressed portion or a projecting portion of the raised and depressed pattern to be formed, wherein when the length of the depressed portion or the projecting portion of the raised and depressed pattern is shorter than a predetermined length, the duty ratio of the pulse-like laser beam is varied in accordance with the length of the depressed portion or the projecting portion of the raised and depressed pattern, and when the length of the depressed portion or the projecting portion of the raised and depressed pattern is equal to or longer than the predetermined length, the duty ratio of the pulse-like laser beam is kept constant independently of the length of the depressed portion or the projecting portion of the raised and depressed pattern, thereby exposing the photosensitive material layer to the laser beam.
5. A method for manufacturing a stamper for a recording medium comprising: forming a raised and depressed pattern including a depressed portion or a projecting portion corresponding to a pit on a photosensitive material layer on or above a light absorption layer provided in a photoresist-coated board by projecting two or more pulses of a laser beam onto the photosensitive material layer to expose the photosensitive material layer thereto and developing the photosensitive material layer; and transferring the raised and depressed pattern formed on the photosensitive material layer onto a stamper for a recording medium and forming a raised and depressed pattern on the stamper, wherein a duty ratio of the pulse-like laser beam is varied in accordance with a length of a depressed portion or a projecting portion of the raised and depressed pattern to be formed, and wherein when a length of a depressed portion or a projecting portion of the raised and depressed pattern is shorter than a predetermined length, the duty ratio of the pulse-like laser beam is varied in accordance with the length of the depressed portion or the projecting portion of the raised and depressed pattern and when a length of a depressed portion or a projecting portion of the raised and depressed pattern is equal to or longer than a predetermined length, the duty ratio of the pulse-like laser beam is kept constant independently of the length of the depressed portion or the projecting portion of the raised and depressed pattern, thereby exposing the photosensitive material layer to the laser beam.
6. A method for manufacturing a recording medium comprising: forming a raised and depressed pattern including a depressed portion or a projecting portion corresponding to a pit on a photosensitive material layer on or above a light absorption layer provided in a photoresist-coated board by projecting two or more pulses of a laser beam onto the photosensitive material layer to expose the photosensitive material layer thereto and developing the photosensitive material laver; transferring the raised and depressed pattern formed on the photosensitive material layer onto a stamper for a recording medium and forming a raised and depressed pattern on the stamper; and transferring the raised and depressed pattern formed on the stamper onto a substrate for a recording medium to form pre-pits on the substrate. wherein a duty ratio of the pulse-like laser beam is varied in accordance with a length of a depressed portion or a projecting portion of the raised and depressed pattern to be formed, and wherein when a length of a pre-pit is shorter than a predetermined length, the duty ratio of the pulse-like laser beam is varied in accordance with the length of the pre-pit and when a length of a pre-pit is equal to or longer than a predetermined length, the duty ratio of the laser beam is kept constant independently of the length of the pre-pit, thereby exposing the photosensitive material layer to the laser beam.
7. A method for manufacturing a recording medium in accordance with claim 6 wherein the duty ratio of the pulse-like laser beam is varied so that the photosensitive material layer is exposed to the laser beam by setting the duty ratio of the pulse-like laser beam to a first value when a pre-pit having a first length is to be formed and that the photosensitive material layer is exposed to the laser beam by setting the duty ratio of the pulse-like laser beam to a second value smaller than the first value when a pre-pit having a second length longer than the first length is to be formed.
8. A method for manufacturing a recording medium comprising: forming a raised and depressed pattern including a depressed portion or a projecting portion corresponding to a pit on a photosensitive material layer provided in a photoresist-coated board by projecting two or more pulses of a laser beam onto the photosensitive material layer to expose the photosensitive material layer thereto and developing the photosensitive material layer; transferring the raised and depressed pattern formed on the photosensitive material layer onto a stamper for an optical recording medium and forming a raised and depressed pattern on the stamper; transferring the raised and depressed pattern formed on the stamper onto a substrate for a recording medium to form pre-pits on the substrate; and varying a duty ratio of the pulse-like laser beam in accordance with a length of a pre-pit to be formed, and wherein when a length of a pre-pit is shorter than a predetermined length, the duty ratio of the pulse-like laser beam is varied in accordance with the length of the pre-pit and when a length of a pre-pit is equal to or longer than a predetermined length, the duty ratio of the pulse-like laser beam is kept constant independently of the length of the pre-pit, thereby exposing the photosensitive material layer to the laser beam.
9. A method for manufacturing a recording medium in accordance with claim 8 , wherein the duty ratio of the pulse-like laser beam is varied so that the photosensitive material layer is exposed to the laser beam by setting the duty ratio of the pulse-like laser beam to a first value when a pre-pit having a first length is to be formed and that the photosensitive material layer is exposed to the laser beam by setting the duty ratio of the pulse-like laser beam to a second value smaller than the first value when a pre-pit having a second length longer than the first length is to be formed.
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March 10, 2003
November 20, 2007
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